An air pollution sensor system is used for monitoring the concentration of airborne pollutants, particularly of health-hazardous airborne pollutants. In combination with a filtration system comprised in an air handling system, an air pollution sensor system can be used to monitor and control the concentration of airborne pollutants inside an enclosure receiving ventilation air from the air handling system.
An air pollution sensor system comprises an air inlet, an air outlet, a sensor unit, and an air displacement device, the air displacement device being arranged to establish an air flow from the air inlet through the sensor unit to the air outlet. The sensor unit functions through interaction with airborne pollutants, for instance by removing airborne pollutants from the air flow using a filter, or by determining the presence of airborne pollutants in the air flow by interaction with electromagnetic radiation.
The sensor unit of the air pollution sensor system according to the invention comprises a filter for removing airborne pollutants from the air flow. As a result, the sensor unit generates an output signal with a magnitude that is proportional to the amount of airborne pollutants that is removed by the filter per unit time.
During operation an increasing amount of airborne pollutants is being deposited in the sensor unit. Consequently, the magnitude of the output signal measured at a certain air pollution level may change over time, for instance because of changing filter or filtration characteristics. The lifetime of an air pollution sensor system is defined as the time after which the magnitude of the output signal measured under a defined set of conditions has changed to a certain percentage (for instance 50%) with respect to the initially measured value in the presence of a clean filter.
An air pollution sensor system comprising a sensor unit and a ventilator for displacing air is known from WO 2006/016346 A1. The sensor unit of the known air pollution sensor system comprises a particle precipitation section. With respect to maintenance issues and the reliability of the output signal, there is an ongoing need to improve the lifetime of such an air pollution sensor system.